track entry to Editor so we can set the current editing context

gtk2_ardour/editor.cc

@@ -702,6 +702,14 @@ Editor::Editor ()
 	setup_fade_images ();
 
 	switch_editing_context (this);
+	contents().signal_enter_notify_event().connect (sigc::mem_fun (*this, &Editor::enter), false);
+}
+
+bool
+Editor::enter (GdkEventCrossing*)
+{
+	switch_editing_context (this);
+	return false;
 }
 
 Editor::~Editor()

gtk2_ardour/editor.h

@@ -2293,6 +2293,8 @@ private:
 	PBD::Signal<void()> VisibleMarkersChanged;
 	PBD::Signal<void()> VisibleRangesChanged;
 
+	bool enter (GdkEventCrossing*);
+
 	friend class RegionMoveDrag;
 	friend class TrimDrag;
 	friend class MappingTwistDrag;